In networking, a "Port" is like a door number for a specific service on a server. If you send a letter to a building but forget the apartment number, it never reaches the right person. Similarly, if you don't open the correct port in your Firewall (AWS Security Group), your application won't work.
Here is the ultimate cheat sheet of the Top 30 Ports used in real-world DevOps environments.
1. Web Access & Remote Control
These are the ports you will interact with almost every single day.
| Port | Service | Use Case (Simple English) |
|---|---|---|
| 20 / 21 | FTP | File Transfer Protocol. Used to upload files (Old school). |
| 22 | SSH | Most Important! Secure Shell. Used to log into Linux servers. |
| 53 | DNS | Converts "google.com" into an IP address (like 8.8.8.8). |
| 80 | HTTP | Standard Web Traffic (Unsecured websites). |
| 443 | HTTPS | Secure Web Traffic (Websites with the Lock icon 🔒). |
| 3389 | RDP | Remote Desktop. Used to log into Windows Servers. |
2. Databases & Storage
When connecting your backend application to a database, you must allow traffic on these ports.
| Port | Database | Use Case |
|---|---|---|
| 1433 | SQL Server | Default port for Microsoft SQL Server. |
| 3306 | MySQL | Most popular open-source DB (WordPress, Facebook). |
| 5432 | Postgres | Advanced open-source DB for enterprise apps. |
| 6379 | Redis | In-memory caching database for speed. |
| 27017 | MongoDB | NoSQL document database. |
3. DevOps & Monitoring Tools
Specific ports for tools you will configure in CI/CD pipelines.
| Port | Tool | Use Case |
|---|---|---|
| 8080 | Jenkins | Default port for Jenkins Dashboard / Tomcat. |
| 9000 | SonarQube | Code quality scanning dashboard. |
| 9090 | Prometheus | Metrics monitoring tool. |
| 9100 | Node Exp | Sends Linux server metrics to Prometheus. |
| 3000 | Grafana | Visual dashboard for metrics. |
| 5000 | Docker | Private Docker Registry / Flask Apps. |
| 5601 | Kibana | Visual dashboard for ElasticSearch logs. |
| 9200 | Elastic | ElasticSearch Database port. |
| 8081 | Nexus | Artifact repository manager. |
Pro Tip: When setting up an AWS Security Group (Firewall), strictly limit access to Port 22 (SSH) and 3389 (RDP) to "My IP Only". Never open them to "0.0.0.0/0" (The World) or you will be hacked!